So what is a “Swirl Destroyer”??

I think the truck has an old 550 V8. These engines (if still original) idle and run low loads on 4 cilinders.
Early engines had the swirl destroyer.

The swirl destroyer knob and cable operated butterfly/throttle valves in 4 of the intake ports.
These valves were to be operated on cold engine to aid starting and warm-up at low loads closing the intake ports on the cilinders that were not firing.

Picture from engine manual:




It was not uncommon to have the fuel pumps modified so the engine ran on all 8 all the time. In that case the swirl destroyer was not to be used.

I've never seen it, but I heard stories of the butterfly valves breaking of or coming loose and being swallowed by the engine. Not a good thing of course.

 

Yes,swirl destroyers,they were on the old DV462/550 IH diesels. Not one of IH's better engines. Poor performance,and I've never seen an engine smoke as much as one of these,esp. on cold start-up. Have taken these apart,and the butterfly valves look like they were burnt off.
In the very early 70's I worked as a diesel mechanic at the factory truck branch in Baltimore. Went out one morning to get a Loadstar with one of these engines in it off our lot to bring in the shop to work on it. After I started it,and was building up air,it smoked so bad traffic stopped on 25th street,people couldn't see where they were going. Someone actually called the fire department,as it smoked up a whole city block.
Operators didn't understand the swirl destroyer,and would just run with it on.

 

You almost made me choke on my coffee... That right there IS FUNNY!!!

 

Thanks,these engines were a real pooch. We had an injection pump room in our shop running non stop,trying to recalibrate and get horsepower for unhappy DV 550 owners. When this engine came out it,it was IH's way to try and get in the mid size diesel market,and compete against Ford,who had rights to the 3208 Cat. IH finally gave up on the DV 550,and made a deal with Cat to use the 3208 also,and finally put the DV 550's out to pasture.

 

You've got to remember this engine was first designed in the 60's when there was still quite a learning curve going on about what make diesels tic. I have some Sheppard Diesels from the 50's that are 22 to 1 compression ratio,and squirt gun injection pressures,they thought that was the key to diesel performance back then. We now know it's just the opposite.
There wasn't much as far as emissions control requirements to speak of back then,and IH's injection,piston and combustion chamber deal was a swirling fuel mixture design theory. Didn't seem to make much power,but did succeed in making boatloads of smoke. The swirl destroyer flaps was supposed to limit the swirl of incoming air,and help reduce smoke when it was cold. Like a diesel choke,fwiw. That combines with the timing and pump calibration being a little off,a little ring wear,dirty air filter,etc.,etc. Made for a machine that turned diesel fuel into eye tearing smoke,lots of it.
The swirl destroyer vanes were on all intake ports as far as I can remember,but it's been at least 45 years since I last worked on one of these beasts,as I left IH around 1974,so I could be wrong. The vanes were just little stamped flat pieces of metal,hooked to a shaft,like a throttle plate in a carburetor. I do remember it was a spring loaded mechanical linkage mess,under the intake,and was a huge PITA to get it all hooked up and functioning.
IH did build some wonderful engines,esp. back in the gasser days. The V 345,392,478,549,and even the big 450,501 Red Diamond 6's gas jobs,were great truck engines. But the DV 550's,at least the early ones,were ones that I think IH would rather forget about.

 

Going off my memory, when I worked on some of these engines, DV550's and the later 9.0 liter out of old army trucks and farm tractors, and some research I did back then.

20-25 years ago, so there may/will be some gaps and mistakes.

Information I found back then is that first engines used a Holley injection pump, later engines used Bosch.

My own observations:

The 9.0L was the successor of DV550, different combustion process, different pistons and fuel system, different block casting. Easiest way the see the difference is the tappet covers. The DV550 casting was open in the middle (above cam and tappets) and had 1 single covers, covering the complete valley between the heads.
9.0L block was closed in the middle (above the camshaft) and has 2 separate covers, left and right, over the tappets.

The DV550's had butterfly valves, but only on 4 cilinders. I remember (but may be wrong here) I saw versions with valves on every cilinder of one bank, no valves on other bank, and also versions which had valves on 2 cilinders of each bank. The 2 different versions also had different fuel pumps.

The tractor engines did not have the swirl destroyers, maybe just because they were of a later production date, and later truck DV550 and 9.0L engines did not use them either.

The pistons in the 9.0L later had the "mexican hat" combustion chambers.

The DV550's used a spherical combustion chamber in the piston (MAN M-type combustion), and a 2 hole injector, 1 small hole and a larger hole.
As far as I could figure out, the small hole injected fuel in the air flow, for "normal" combustion.
The large hole injected fuel onto the wall of the spherical combustion chamber, high swirl of the intake air helped to deposit a film of fuel onto the combustion chamber wall. When hot, the film of fuel would evaporate and result in a gradual combustion and slower pressure rise making the engine run more quietly and smoother.

On a cold engine, the fuel would not evaporate fast enough from the wall, and did not contribute much to the combustion, but would result in lots of white smoke. Not only on the IH engines, others that used the same combustion process as well (in Europe old MAN, Berliet come to mind)

My opinion is that the swirl destroyer's main task was to change the direction/shape of the air flow into and inside the cilinder, in an attempt to limit the amount of fuel deposited on the combustion chamber wall.

As I said at the beginning, all from memory, and it was many years ago......and maybe not all of the engines were still original. They were already old back then.